Aqueous-triggered color-appearing inks

ABSTRACT

The invention describes a color-developing composition that contains at least four major components: (1) a leuco dye or a combination of leuco dyes, (2) an electron-withdrawing color-developer agent or a combination of color-developers that can form colored complexes with the leuco dyes, (3) a separator or combination of separators that when present in sufficient amounts, can prevent the formation of the colored complexes between the color-developer and leuco dyes, all contained within (4) an encapsulation matrix that includes at least one film-forming and one aqueous-insoluble polymer. All of the foregoing components are dissolved together in a volatile organic solvent medium to form a homogeneous solution that can be applied as an ink on substrates, which can be incorporated as part of absorbent articles or personal care products.

FIELD OF INVENTION

The present invention pertains to an indicating composition for anaqueous medium. In particular, the present invention describes a mediumor ink that can change from being colorless to color in the presence ofan aqueous solution.

BACKGROUND

Many products, including consumer, health care, and professionalproducts, are more effectively used by an end user when the productincludes a feature that can communicate or signal to the user aparticular condition or indicate the relative level or degree of use. Anexample is a visual indicator that causes the product to change color orappearance. Color indicators can either indicate a change in conditionor a degree of use through a change from “no color” to “color” (or viceversa) or through a change from one color to a different color.

Exemplary conditions that could be monitored using a color indicatorinclude physical conditions such as the presence of moisture andchemical conditions such as a change in pH. Exemplary consumer productsthat could be more effective and deliver more benefits to end users byincorporating a suitable color indicator include absorbent articles,facial tissues, bath tissue, paper towels, household cleaning items andpersonal cleaning wipes. Exemplary professional products that could bemore effective and deliver more benefits to end users by incorporating asuitable color indicator include products for medical use, safetygarments, industrial cleaning products and nonwoven materials.

Color indicators are well known and are available in various forms.Desirable performance attributes include durability and good retention(i.e. the color indicator remains where intended and does not leach outinto other components of the product within which it is being used).Depending on the product application, it may also be desirable to havethe structure in which the color indicator is used to be wettable, butwater insoluble. For purposes of applying the color indicator to acomponent of a product, it may also be desirable to have a colorindicator that can be applied in liquid form at room temperature. Whenthe color indicator is in a liquid form at room temperature, the colorindicator can be printed (just like an ink composition) onto the desiredcomponent of a product.

Examples of the color indicators that have been already incorporatedinto consumer products include diapers that have wetness sensors. Someof the wetness sensors used in diapers change color to indicate wetnesswhile others lose color in response to wetness (i.e. the color fades ordisappears when it is dissolved by water). The concept of incorporatinga color-changing composition into a wearable article (such as adisposable diaper) is known in the art. For example, U.S. Pat. No.7,159,532 issued to Klofta et al. (hereinafter “the '532 patent”) isdirected to wetness indicating compositions having improved colorantretention and durability for use with wearable articles. The wetnessindicating compositions of the '532 patent have a first binding agentand a second binding agent. The first binding agent immobilizes acolorant when the colorant is in its initial color state and the secondbinding agent immobilizes the colorant when the colorant is in its finalcolor state. The component materials used in the examples provided inthe '532 patent are solid at room temperature as indicated by thedescription that they need to be melted by heating in order to combinethem. While the wetness indicating compositions of the '532 patent arecapable of changing color in response to a stimulus, they are notcapable of being applied to an article in liquid form at roomtemperature.

While the color-changing compositions known in the art provide certainbenefits, there remains a need for a film-forming composition that canbe applied to a substrate. There also remains a need for a compositionthat is durable, has good retention and that shows rapid and dramaticcolor change when the composition is used in a product. When the purposeof the composition is to detect the presence of wetness, there remains aneed for a composition that is water-resistant and water-insoluble.Further, there remains a need for a composition that can be applied,such as by printing, at room temperature so that the composition can beapplied to a substrate without heating.

SUMMARY OF THE INVENTION

The present invention relates in part to a color-developing compositionor molecular system for use in an indicator medium or ink solution. Thecolor-developing composition in ink form can form thin films of variouspatterns and shapes on a substrate upon drying and the films cangenerate color upon contact with an aqueous medium. The solutioncomposition or molecular system includes at least four-components alldissolved in a volatile organic solvent medium. The four components arean assembly of: 1) a leuco dye or a combination of leuco dyes, 2) anelectron-withdrawing color developer or a combination ofcolor-developers that can form color complexes when associated with theleuco dye under the proper conditions, and 3) a separator or combinationof separators, which when dissolved in the system in an adequatequantity, can prevent the formation of the colored complexes, allcontained within 4) an polymeric encapsulation matrix. The encapsulationmatrix is composed of at least a film-forming and water insolublepolymer. The composition may be part of an indicator medium that is anorganic solvent-based wetness ink. The ink in its original state iscolorless and the films formed from the inks upon evaporation of theorganic solvents are also colorless because no water is present in theoriginal solution to interact with the components. The presence orintroduction of water to the dried films will activate the compositionto trigger color manifestation. The present invention belongs to a classof organic-solvent based wetness indicating inks that can form thinfilms on various substrates when dried, and the films can achieve rapidand dramatic color appearing upon wetting, such as when in contact withan aqueous-based fluid like urine. The inks can be applied to varioussubstrates such as polyethylene films by means of various techniquessuch as flexographic and gravure printing.

In another aspect, the invention is a colorless or pale-colored,non-aqueous-based, homogeneous solution having a composition comprising:a) one or more leuco dyes; b) one or more separators or desensitizersthat are non-volatile and are significantly soluble in both volatileorganic solvents and water; c) one or more electron withdrawingcolor-developers that cannot form colored complexes with said leuco dyesin the presence of a significant amount of the separators without thepresence of water, but can form colored complexes with the leuco dyes inthe presence of water, wherein said composition is in an encapsulationmatrix that is insoluble in water, but soluble in volatile organicsolvents. The composition may also include one or more volatile organicsolvents.

In yet another aspect, the invention is related to an indicator or adevice for wetness sensor that has a solid surface to which thehomogeneous solution can be applied or printed.

Further, the invention also relates to an absorbent article thatincorporates at least one component that has the homogeneous solutionapplied or printed on it.

Additional features and advantages of the present molecular system andhomogeneous composition will be described in the following detaileddescription. It is understood that the foregoing general description andthe following details description and examples are merely representativeof the invention, and are intended to provide an overview forunderstanding the invention as claimed.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a schematic representation of the initial relationship of thethree components (leuco dye, electron-withdrawing developer, andseparator or desensitizer agent) in the molecular system according tothe present invention, and how the three components of the molecularsystem function with each other when encapsulated.

FIG. 2 is a schematic illustration of how the three components in themolecular system interact to develop color from an initial colorlessappearance when exposed to an aqueous solution or solvent.

FIG. 3A-3C is a series of illustrations of a polymeric film or nonwovenfabric or web substrate that is printed with an ink compositioncontaining the present molecular system. FIG. 3A shows the substrate atan initial stage with a largely colorless appearance. FIG. 3B show thesame substrate immediately after an aqueous solution is applied to theink-printed region of the substrate. FIG. 3C shows the development ofcolor as the aqueous solution more fully reacts with the molecularsystem in the ink composition.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in part to a homogeneous solution having acomposition that includes multiple-components. The homogenous solutioncan be applied as an ink material, by means of conventional printingtechniques, to a substrate surface and can form part of a film layer onthe substrate. The composition can be applied as a single-phase solutionthat solidifies into a thin, self-assembled film or matrix uponevaporation of solvents. The film layer includes a color-developingcomposition that can cause the film layer to change from a largelycolorless or pale appearance to a visually distinct or vibrant colorwhen the film layer is exposed to a change in its immediate physical orchemical environment as a result of the introduction of an aqueousmedium or mixture.

Section I—Color-Developing Composition or Molecular System

The present invention involves a color-developing composition ormolecular system that contains at least four major components: (1) aleuco dye or a combination of leuco dyes, (2) an electron-withdrawingcolor-developer agent or a combination of color-developers that can formcolored complexes with the leuco dyes, (3) a separator or combination ofseparators that when present in sufficient amounts in the system, canprevent the formation of the colored complexes between thecolor-developer and leuco dyes, all contained within (4) anencapsulation matrix that includes at least one film-forming and oneaqueous-insoluble polymer. The encapsulating matrix contains at leastone kind of polymeric resin that can form a thin film on plasticsubstrate surfaces with good adhesion. All of the foregoing componentsare dissolved together in a volatile organic solvent medium to form ahomogeneous solution. The leuco dye, color-developing agent andseparator components are not phase-separated from each other in thesolution.

In addition to the four main components, the solution may also containother additives to adjust their physical properties. The composition maycontain reagents to adjust the viscosity of the solution, or may includechemicals to improve adhesion of the composition to certain substratesurfaces upon drying. The composition may also have chemicals thattailor the composition's subsequent wettability on the substratesurface.

FIG. 1, is a schematic representation of the initial relationship of thecomponents within the polymeric encapsulation matrix. The leuco dye 1and color-developer agent 2 are separated from reacting with each otherby the separator 3 within the encapsulation 4. The leuco dye andcolor-developer agent used in the composition exhibit good solubility inorganic solvents, but poor solubility in aqueous media. On the otherhand, the separator exhibit good solubility in both an aqueous andorganic solvent.

Although not bound by theory, FIG. 2, is a theoretical, schematicillustration of how between the individual components interact with eachother to develop color. It is speculated that the leuco dye 1 and thecolor-developer agent 2 are separated from each other by the separator 3when the composition is dried by means of solvent evaporation on asubstrate to show a colorless or a pale, weakly colored state. The leucodye and color-developer are capable of interacting to manifest colorwhen the separator dissolves or disperses in the presence of an aqueoussolution. Upon wetting or when the liquid pervious encapsulation matrixencounters an aqueous-based solution, the fluid enters the capsule 4.Some of the separator 3 is either dissolved or dissociated from thecomplex into the aqueous medium. The water molecules penetrate into theencapsulation to make the micro-environment more hydrophilic. This eventpermits the other two other components, leuco dyes molecules 1 tointeract with the color-developer agent 2 to form colored complexes 10.

Leuco dyes are generally referred to as colorless or pale-colored basicdyes, because the dye molecules can acquire two forms, one of which iscolorless. Although not intended to be bound by theory, it is believedthat the color-developer agent functions as a Lewis acid, whichwithdraws electrons from the leuco dye molecule to generate a conjugatedsystem. Hence, the leuco dye appears to manifest color from anoriginally colorless state.

For example, the spiro Form of an oxazine is a colorless leuco dye; theconjugated system of the oxazine and another aromatic part of themolecule is separated by an sp³-hybridized “spiro” carbon. Afterprotonating a part of the molecule, irradiation with UV-light orintroducing other kind of such change, the bond between the spiro carbonand the oxazine interrupts, the ring opens, the spiro carbon achievessp² hybridization and becomes planar, the aromatic group rotates, alignsits π-orbitals with the rest of the molecule, and a conjugated systemforms, with ability to absorb photons of visible light, and thereforeappear colorful.

The leuco dyes that may be employed can be selected from a variety ofdyes including, for example, phthalide leuco dyes, triarylmethane leucodyes, and fluoran leuco dyes. Examples may include (1)Triarylmethane-based dyes, e.g.3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide,3,3-bis(p-dimethylaminophenyl)phthalide,3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide,3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide,3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide,3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide,3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide,3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide,3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide,etc. (2) Diphenylmethane-based dyes, e.g.,4,4′-bisdimethylaminobenzhydryl benzyl ether, N-halophenylleucoauramine,N-2,4,5-trichlorophenyl-leucoauramine, etc. (3) Lactam-based dyes, e.g.,rhodamine-B-anilinolactam, rhodamine-(p-nitroanilino)lactam,rhodamine-(o-chloroanilino)lactam, etc. (4) Fluoran-based dyes, e.g.,3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran,3-di-ethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran,3-diethylamino-6-methyl-7-chlorofluoran,3-di-ethylamino-6,7-dimethylfluoran,3-(N-ethyl-p-toluidino)-7-methylfluoran,3-diethylamino-7-(N-acetyl-N-methylamino)fluoran, fluoran,3-diethylamino-7-(N-methylamino)fluoran,3-diethylamino-7-dibenzylaminofluoran,3-diethylamino-7-(N-methyl-N-benzylamino)fluoran,3-diethylamino-7-(N-chloroethyl-N-methylamino)fluoran,3-diethylamino-7-N-diethylaminofluoran,3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran,3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino) fluoran,3-diethylamino-6-methyl-7-phenylaminofluoran,3-dibutylamino-6-methyl-7-phenylaminofluoran,3-diethylamino-7-(2-carbomethoxyphenylamino) fluoran,3-(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluoran,3-pyrrolidino-6-methyl-7-phenylaminofluoran,3-piperidino-6-methyl-7-phenylaminofluoran,3-diethylamino-6-methyl-7-(2,4-dimethylamino)fluoran,3-diethylamino-7-(o-chlorophenylamino)fluoran,3-dibutylamino-7-(o-chlorophenylamino)fluoran,3-pyrrolidino-6-methyl-7-(p-butylphenylamino) fluoran,3-(N-methyl-N-n-amylamino)-6-methyl-7-phenylaminofluoran,3-(N-ethyl-N-n-amylamino)-6-methyl-7-phenylaminofluoran,3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofuluoran,3-(N-methyl-N-n-hexylamino)-6-methyl-7-phenylaminofluoran,3-(N-ethyl-N-n-hexylamino)-6-methyl-7-phenylaminofluoran,3-(N-ethyl-N-β-ethylhexylamino)-6-methyl-7-phenylaminofluoran, etc. Thebasic dyes useful in this invention are not limited to those exemplifiedabove, and at least two of them can be used in admixture.

The separator or desensitizer can be any of known component agent whichexhibit good solubility in both water and organic solvents. Generally,the separators are preferred to be neutral molecules that are without acharge, such as polyalkylene glycol of <1000 Daltons, polyalkylene oxideof <10000 Daltons, block copolymers of polyoxyethylene polyoxypropyleneglycol, polyoxyethylene nonylphenyl ether, polyoxyethylene distyrenatedphenyl ether, neutral surfactants. Other examples of such separators mayinclude glycerin; dodecylamine; 2,4,4-trimethyl-2-oxazoline; polyolefinglycols such as polyethylene glycol, polypropylene glycol and copolymerof ethylene glycol and propylene glycol; polyoxyethylene lauryl ether,polyoxyethylene oleyl ether, polyoxyethylene nonyl phenyl ether,polyoxyethylene sorbitan monolaurate, polyethylene glycol monostearate.

Generally, the color-developers exhibit good solubility in organicsolvents. Examples of suitable developers include bisphenol A, zincchloride, zinc salicylate, and phenol resins. Other examples of colordeveloping materials to be used conjointly with the lecuo dyes mayinclude: 4-tert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol,4-tert-octylphenol, 4,4′-sec-butylidenephenol, 4-phenylphenol,4,4′-dihydroxydiphenylmethane, 4,4′-isopropylidene diphenol,hydroquinone, 4,4′-cyclohexylidene diphenol, 4,4-dihydroxydiphenylsulfide, 4,4′-thiobis(6-tert-butyl-3-methylphenol),4,4′-dihydroxydiphenyl sulfone, hydroquinone monobenzyl ether,4-hydroxybenzophenone, 2,4-dihydroxybenzophenone,2,4,4′-trihydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone,dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl4-hydroxybenzoate, propyl 4-hydroxybenzoate, sec-butyl4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate,benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate, p-methoxybenzyl4-hydroxybenzoate, novolak type phenol resins, phenol polymers and likephenol compounds.

Wetness indicating inks from colorless to various colors have beenhighly desirable for a variety of personal care and health care-relateduses, for instance, personal care products such as diapers or adultincontinence articles. However, no practical wetness indicating inks arecommercially available. Unlike some water-sensitive coloring sheets,such as described in U.S. Pat. No. 5,130,290, relating to a water-basedwetness indicating compositions that are suspensions and not homogenoussolutions on paper or pulp-fiber based substrates, the presentcomposition is solution-based and homogeneous. The composition describedby the '290 patent is water-based and requires heat-drying. Thecompositions are suspension and inhomogeneous, not a solution-based ink.

The present composition can be incorporated as part of an organicsolvent-based wetness indicating ink All the components in the inks aresoluble in an organic solvent or a mixing organic solvent system and theinks are homogeneous. The ink can induce a dramatic visual appearancechange in color in the range of ΔE values of at least 5 or 10, to about20-40-60. Typically, depending on the active component concentration andamount of urine or other liquid disruption, the color will be eliminatedwithin well under 5 or 10 minutes. According to certain examples thecolor is discharged within about 6 minutes, or for faster action withinabout 3 minutes after application of the composition to a stain. One canobserve that the color of the discoloration or stain is reduced by ≧5.In certain other embodiments, the observable color of the stain isreduced by at least a ΔE value of 15 or 20, which lightens the stain tobeing virtually imperceptible by the naked eye. Typically, thediscoloration or stain can be reduced by a ΔE value of about 25-40,desirably up to about 50 to 70 or 80. As will be described in furtherdetail, ΔE is the measurement of color change as defined by 3D colorspace measurements.

Section II—Molecular System Encapsulate

According to the present invention, the composition also includes awater pervious organic polymeric cage or matrix that encapsulates themolecular system. The encapsulation matrix contains at least one polymerthat is soluble in organic solvents, but is not well adapted or solublein aqueous media. The polymers can be a copolymer, block copolymer,linear polymer or random copolymer, or combinations thereof. Thepolymers can be natural polymers, synthetic polymers, and hybridpolymers of the two. The encapsulation matrix should be able to formstable films on various substrates upon drying, particularly after airdrying.

Examples of suitable polymers may include, for instance, Gantrez seriespolymers from International Specialty Products, Inc., Dermacryl 97 fromNational Starch, and Amphomers from Akzo Nobel. The encapsulation matrixmay also be a mixture of various chemicals dissolved in an organicsolvent system. Examples of such a system may include organicsolvent-based varnishes, such as varnishes made by Sunchemical Co.Examples of polymers and copolymers that are substantially soluble inorganic solvents may include: styrene-butadiene copolymers, acrylic acidester polymers, polyvinyl acetates, polyvinyl chlorides;polyvinylbutyral, polyvinyl acetate, vinyl chloride-vinyl acetatecopolymer, acrylic resin, styrene resin, polyester resin, and polyvinylacetate, vinyl chloridevinyl acetate copolymer, styrene-maleic anhydridecopolymer, isobutylene-maleic anhydride copolymer, polyvinyl butyral.

According to the invention, the composition also contains a volatileorganic solvent system. Examples of such volatile organic solvents or amixing solvent system may include low-molecular weight alcohols, such asbutanol, ethanol, propanol, and acetone or tetrahydrofuran or theirmixtures.

Section III—Ink Medium

As stated before, the invention involves a colorless or pale-colored,non-aqueous-based, homogeneous solution having a composition comprising:a) one or more leuco dyes; b) one or more separators or desensitizersthat are non-volatile and are significantly soluble in both volatileorganic solvents and water; c) one or more electron withdrawingcolor-developers that cannot form colored complexes with said leuco dyesin the presence of a significant amount of said separators without thepresence of water, but can form colored complexes with the leuco dyes inthe presence of water, wherein said composition is in an encapsulationmatrix that is insoluble in water, but soluble in volatile organicsolvents. The composition may include one or more volatile organicsolvents.

The volatile organic solvents may include, for example, ethanol,methanol, propanol, isopropanol, butanol, acetone, tetrahydrofuran(THF), benzene and toluene, methylene chloride, chloroform, orcombinations thereof.

In another aspect of the present invention, the encapsulatedcolor-developing component molecular system can be mixed into ahomogeneous solution to form an ink. The ink can be applied to thesurface of plastic substrates, such as polyethylene, polypropylene, orother polyolefins.

The ink has a composition of a volatile organic-based solvent or amixture of different volatile organic solvents, a immobilizationcomposition that includes at least one organic soluble but waterinsoluble film forming polymer or copolymer, a leuco dye and acolor-developer agent both of which are soluble only in organic solvent,and a separator that are soluble in both organic solvent and water. Theink is originally colorless in the absence of water, and manifests colorwhen water is present.

The leuco dyes can be present in the composition from about 0.01 wt. %to about 10 wt. %. Typically the amount of leuco dye can be betweenabout 0.05 or 0.1 wt. % to about 4 or 5 wt. %, or 6 or 7 wt. %;desirably the range is between about 0.5 or 1 wt. % to about 2.5, 3 or 5wt. %, inclusive. The amount of separators typically are present fromabout 1 wt. % to about 20 wt. % or 25 wt. %. Alternatively, theseparators can be present from about 1.5, 2, or 3 wt. % to about 15, 17,or 18 wt. %, inclusive. The amount of developers that are present canrange from about 0.5 wt. % or 1 wt. % to about 10 wt. % or 12 wt. %;typically, between about 1 or 2 wt % to about 7, 8 or 10 wt %. Thepolymeric resin in the encapsulation matrix is present from about 10 wt.% to about 80 wt. %. Typically, the amount of polymer resin is betweenabout 12, 15, or 20 wt % to about 65, 70, or 78 wt. %, inclusive. Thevolatile organic solvents can be present from about 20 wt. % to about 90wt. %; typically between about 25, 30, or 35 wt % to about 80, 85, or 88wt %, inclusive.

Section IV—Printed Articles

The homogeneous wetness inks can be printed on various materialsubstrates, such as plastics, polyethylene or polypropylene films, orcellulose-based papers and tissues. The inks can be air-dried to show acolorless or nearly colorless state of appearance (i.e., either no coloror very weak background shade). The dried inks show various colors uponbeing wetted depending on the kind of leuco dye used. For example, thefilm layer may be on a nonwoven material that is used as a component ofan absorbent article.

The water-insoluble, film-forming polymer and the other components ofthe color-changing composition can be dissolved in the organic solventprior to application onto the substrate. When the mixture of thecolor-changing composition and the organic solvent is formed, themixture is liquid at room temperature. The volatile organic solventevaporates when the color-changing composition is either applied to thefilm layer or forms the film layer. Suitable water-insoluble,film-forming polymers include acrylate/acrylamide copolymers,polyurethane adhesives, copolymers of vinylpyrrolidone and copolymers ofdimethyl aminopropyl methacrylamide. Commercially-available suitablepolymers include DERMACRYL 79 polymer and AMPHOMER HC polymer, both ofwhich are acrylate/octylacrylamide copolymers available from Akzo Nobel.Another example of a commercially-available suitable polymer is GANTREZSP polymer, which is a mono-alkyl ester of poly(methyl vinylether/maleic acid) copolymer available from International SpecialtyProducts, Inc. The color-changing compositions of the invention includea water-insoluble, film-forming polymer in an amount of from 20% to 95%of the total weight of the color-changing composition. Desirably, thecolor-changing compositions of the invention include a water-insoluble,film-forming polymer in an amount of from 60% to 90% of the total weightof the color-changing composition.

Once the homogeneous solution are printed and dried on the surface ofthe substrate, the dried solution can form thin films that can manifestcolor when they contact a water-containing medium. According to certainembodiments, it is desirably that the thin films either cover or form apattern on a visually perceivable surface of the substrate. This featurewould be useful when the printed substrate is part of either anabsorbent article or a personal care product formed with the substratethat may contact an aqueous solution or urine. The absorbent article mayfor example be a diaper, feminine hygiene pad, adult incontinencearticle, or wiper cloth.

The article may comprise a polymeric film or nonwoven substrate surfacehaving at least a portion of said substrate surface printed with acolor-developing medium that contains a complex formed from a leuco dye,a electron-withdrawing color-developer agent, and a separator, allcontained within an aqueous-pervious polymeric matrix, where saidseparator is soluble in both an aqueous and organic solvent, and saidleuco dye and color-developer are capable of interacting to manifestcolor when said separator dissolves or disperses in the presence of anaqueous solution. The substrate can be either a porous film ornon-porous film, or a combination of both kinds of films. The porousfilms may include cellulose based tissue, papers, nonwoven materials, orbreathable films, such as polyethylene and polyproplylene films imbeddedwith calcium carbonate.

FIGS. 3A-3C are illustrations that show a substrate surface, which maybe either porous or non-porous, polymeric or cellulose-based, that hasbeen printed with ink according to the present invention. FIG. 3A showsthe substrate at an initial stage with a largely colorless appearance.FIG. 3B shows the same substrate immediately after the printed areacontacts an aqueous-based fluid. FIG. 3B shows the further developmentof color as either more aqueous-based fluid is applied or spreads morefully over the printed area, and interacts with the presentcolor-developing composition.

Section V—Empirical

EXAMPLE 1

To each of six glass vials (labeled as vial 1, 2, 3, 4, and 5,respectively) was added with 500 ul of crystal violet lactone (12 mg/ml)in ethanol and 500 ul of biphenol A (50 mg/ml) in ethanol. A differentamount of polyethylene glycol (PEG, MW: 200), ranging from 18, 30, 60,120 and 18 mg, was added to vial 1, 2, 3, 4 and 5, respectively. To eachof the vials was further added 2 ml Varnish from Sunchemical Co. and themixtures were vortexed for 2 minutes. To vial 6, 100 ul of benzetheniumchloride in ethanol (50 mg/ml) was added and mixed well. The mixture ineach vial was used to form a thin film on a polyethylene film using abrush and the thin film was then air-dried for 4 hours. The color of thefilm from each vial is slightly blue, slightly blue, colorless,colorless and blue for vial 1, 2, 3, 4, and 5, respectively. Uponwetting with water or synthetic urine, all the films became blue within5 minutes.

EXAMPLE 2

The ink from vial 4 in example 1 was applied to printer-copy paper fromXEROX, KLEENEX®-brand tissue from Kimberly-Clark and were air-dried for5 hours. The color of the paper and tissue was white. The paper andtissue became blue upon in contact with water or synthetic urine.

EXAMPLE 3

About 25 mg zinc salicylate and 120 mg polyethylene glycol (molecularweight: 200) were added to 500 ul of crystal violet lactone (12 mg/ml)in ethanol. The mixture was blue. 1 ml varnish was added and the colorremains blue. The ink was brusheded on polyethylene film and air-dried.The dried film remains blue. No color change was observed upon incontact with water or synthetic urine. Using 25 mg benzentheniumchloride to replace the PEG makes the ink even more blue.

EXAMPLE 4

About 1 ml crystal violet lactone (20 mg/ml) in acetone was mixed with500 ul of benzethenium chloride in ethanol (50 mg/ml). 1 mlSUnchemical's varnish was added and mixed to make an ink. The ink wasbrushed on polyethylene film to form a thin film. The thin film wasdried and show weak blue color. The weak blue color became deep blueupon wetting with water or synthetic urine.

EXAMPLE 5

About 6 mg crystal violet lactone, 18 mg biphenol A and 72 mg Tween 20were dissolved in 1 ml ethanol. 1 ml Sunchemical varnish was added tothe solution and mixed well. The solution was brushed on polyethylenefilm and air dried. The film shows white. The white color did not changeupon contact with water or synthetic urine.

EXAMPLE 6

About 250 μl crystal violet lactone (24 mg/ml in acetone) was mixed withbiphenol A in ethanol (50 mg/ml). 250 μl Sunchemical varnish and 500 μlPEG (75 mg/ml, MW: 1000) in acetone were added and mixed. The solutionwas brushed on polyethylene film and showed no color upon air-drying.The film has no significant color change upon wetting with water orsynthetic urine. Using PEG (MW: 5000) to replace PEG (MW: 100) resultsin the film that did not change color upon wetting.

EXAMPLE 7

About 500 μl crystal violet lactone (24 mg/ml) in acetone, 500 μl zincsalicylate (100 mg/ml) in ethanol and 1 ml varnish were mixed well. Themixture was equally divided into four portions, each in a vial,designated as vial 1, 2, 3, and 4, respectively. To vial 1, 2, 3 and 4was added 0, 100 μl, 200 μl and 400 μl of benzenthenium chloride (50mg/ml) in isopropanol, respectively. The mixture in each vial wasbrushed on polyethylene film and air-dried. The film color made of themixture from vial 1, 2, 3 and 4 is deep blue, deep blue, moderately blueand weak blue, respectively. Upon wetting with water or synthetic urine,the color remains the same for the samples from Vial 1 and 2. Slightlydiscoloring was observed for the film from Vial 3. Significantlydiscoloring was observed for the sample from Vial 4.

EXAMPLE 8

About 500 μl crystal violet lactone (24 mg/ml) in ethanol, 500 μlbiphenol A (50 mg/ml) in ethanol and 60 ul PEG (MW: 200) were mixedwell. 1 ml Sunchemical varnish was added and mixed well. The mixture wasapplied to an outer cover film with a spunbond layer and air-dried toshow a slightly blue color. The piece was used to cover a rectangularhole cut from a new-born diaper on the outer cover. The ink film was incontact with the superabsorbent core through tapes. 10 ml of syntheticurine added to the diapers in the center causes the film to change todeep blue.

EXAMPLE 9

About 500 μl ORC Red KC from Organic Dyestuff Co. (16 mg/ml) in acetoneand 500 ul diphenol A (50 mg/ml) in ethanol was mixed. 200 ul PEG (MW:200) was added and mixed well. The mixture was then added with 1 mlvarnish and mixed well. The color of the mixture was slightly red. Themixture was applied to a piece of spunbond coated polyethylene film andair-dried to show slightly pink color. The film became intensely pinkupon in contact with water or synthetic urine. Using PEG (MW: 1000) toreplace PEG (MW: 1000) resulted in the film that did not change uponwetting.

EXAMPLE 10

Five vials, each containing 500 μl of crystal violet lactone (12 mg/ml)in ethanol and 500 ul of biphenol A (50 mg/ml) in ethanol and 500 μl oforganic-solvent based varnish (from Sunchemical). In addition, 18 mg, 30mg, 60 mg, 120 mg, 120 mg of polyethylene glycol (MW: 200) was added tovial 1, 2, 3, 4 and 5, respectively. To vial 5, 100 μl of benzethoniumchloride in ethanol was added. The mixtures were bath-sonicated for 5minutes. A small amount of each mixture was applied to a polypropylenefilm to form a thin film. The films were air dried. The color of thefilm from vial 1, 2, 3, 4, and 5 are slightly blue, slightly blue, traceof blue, colorless and colorless, respectively. The color of the filmformed by the mixture in vial 1, 2, 3, 4 and 5 all changed to blue uponin contact with synthetic urine.

EXAMPLE 11

Five vials, each containing about 500 μl of crystal violet lactone (12mg/ml) in ethanol and 500 ul of biphenol A (50 mg/ml) in ethanol and 500μl of organic-solvent based varnish (from Sunchemical). In addition, 18mg, 30 mg, 60 mg, 120 mg, 120 mg of polyethylene glycol (MW: 200) wasadded to vial 1, 2, 3, 4 and 5, respectively. To vial 5, 100 μl ofbenzethonium chloride in ethanol was added. The mixtures werebath-sonicated for 5 minutes. A small amount of each mixture was appliedto a polypropylene film to form a thin film. The films were air dried.The color of the film from vial 1, 2, 3, 4, and 5 are slightly blue,slightly blue, trace of blue, colorless and colorless, respectively. Thecolor of the film formed by the mixture in vial 1, 2, 3, 4 and 5 allchanged to blue upon in contact with synthetic urine.

The present invention has been described both generally and in detail byway of examples and the figures. Persons skilled in the art, however,can appreciate that the invention is not limited necessarily to theembodiments specifically disclosed, but that substitutions,modifications, and variations may be made to the present invention andits uses without departing from the spirit and scope of the invention.Therefore, changes should be construed as included herein unless themodifications otherwise depart from the scope of the present inventionas defined in the following claims.

I claim:
 1. A colorless or pale-colored, non-aqueous-based, homogeneous solution comprising: a) one or more leuco dyes; b) one or more separators that are non-volatile and soluble in both volatile organic solvents and water; c) one or more electron withdrawing color-developers that cannot form colored complexes with said leuco dyes in the presence of said separators without the presence of water, but can form colored complexes with the leuco dyes in the presence of water; wherein the solution is in a water-pervious, organic polymeric cage that comprises at least one polymer that is soluble in volatile organic solvents.
 2. The homogenous solution according to claim 1, wherein said polymeric cage comprises a polymeric resin.
 3. The homogeneous solution according to claim 1, wherein said composition includes one or more volatile organic solvents.
 4. The homogeneous solution according to claim 1, wherein said one or more leuco dyes are present from about 0.01 wt. % to about 10 wt. %; said one or more separators are present from about 1 wt. % to about 25 wt. %; said one or more developers are present from about 0.5 wt. % to about 12 wt. %.
 5. The homogeneous solution according to claim 1, wherein a polymeric resin is present from about 10 wt. % to about 80 wt. %.
 6. The homogeneous solution according to claim 1, wherein said one or more volatile organic solvents are present from about 20 wt. % to about 90 wt. %.
 7. The homogeneous solution according to claim 1, wherein said leuco dyes are selected from phthalide leuco dyes, triarylmethane leuco dyes, and fluoran leuco dyes.
 8. The homogeneous composition according to claim 1, wherein said separators include neutral components that are without a charge.
 9. The homogeneous solution according to claim 8, wherein said separators are selected from the group consisting of polyalkylene glycol of <1000 Daltons, polyalkylene oxide of <10000 Daltons, block copolymers of polyoxyehtylene polyoxypropylene glycol, polyoxyehtylene nonylphenyl ether, polyoxyethylene distyrenated phenyl ether, and neutral surfactants.
 10. The homogeneous solution according to claim 1, wherein said color-developers are selected from the group consisting of bisphenol A, zinc chloride, zinc salicylate, and phenol resins.
 11. The homogeneous solution according to claim 1, wherein volatile organic solvents are selected from the group consisting of ethanol, methanol, propanol, isopropanol, butanol, acetone, tetrahydrofuran (THF), benzene and toluene, methylene chloride, chloroform, and combinations thereof. 